The present invention relates to a device used in performing trial reduction in joint arthroplasty such as total hip arthroplasty.
The operation of one type of joint arthroplasty, hip arthroplasty, includes a step of removing a natural femoral head from its femoral shaft and acetabulum. In the hip arthroplasty procedure, the femoral shaft is typically rotated for better exposure. Next, a femoral shaft osteotomy is performed. In this procedure, the head is cut away from the femur.
The femoral shaft encloses an intramedullary canal, bordered by an annular femoral wall that is reamed and broached to accommodate a hip stem prosthesis. Once the annular wall of the canal has been reamed and broached, an acetabular socket component of the hip replacement prosthesis is positioned.
Preparing the femoral shaft for receiving the hip stem prosthesis has required many tools. The Forte U.S. Pat. No. 4,306,550, describes tools usable for preparing a socket and a femur for receiving a femoral prosthesis. The tools include a broach having a cutting portion and a post portion, a handle assembly with a chuck for releasably engaging the post portion to facilitate working the broach into a femur and a guide plate adapted to be journaled on the post. After a cavity is formed in the femur by use of the broach, the broach remains in the socket.
Before inserting a final femoral hip stem into the canal, a surgeon typically inserts a trial femoral stem, neck and head component in order to perform a range of motion trial. In this trial, the surgeon checks the articulation of the trial femoral component with the acetabular socket. Also, the surgeon uses trial reduction to select a proper femoral neck length in order to correct for any leg length discrepancy that a patient may display.
Previous devices used in trial reduction in hip arthroplasty have relied upon a use of a trial prosthesis with a fixed neck length which is fully inserted into the intramedullary canal of the reamed femur. This type of trial prosthesis has required many components in order to have a full array of combinations of prosthesis sizes and neck lengths.
One modification of this trial is described in U.S. Pat. No. 4,601,289 ('289). The '289 patent describes attaching a provisional head or neck onto a broach assembly. Such an attachment eliminates an extra step of inserting an additional femoral component. The attachment also reduces the quantity of components needed to make an instrumentation set. Undesirably, this type of device still requires numerous head and neck components to perform trials for all neck lengths and head combinations.